Galvanic anode installation



Dec. 25, 1956 R. c. JORGENSEN 2,775,554

' GALVANIC ANODE INSTALLATION Filed April 29, 1954 1N VENTOR Ray C.Jorge/wen BY 5 z 3 g ATTORNEYS.

United States Patent() GALVANIC ANODE INSTALLATION Roy C. Jorgensen,Lake Jackson, Tex., assignor to The Dow Chemical Company, Midland,Mich., a corporation of Delaware Application April 29, 1954, Serial No.426,518

4 Claims. (Cl. 204-197) This invention relates to the cathodicprotection of metallic surfaces against electrolytic corrosion, andparticularly to means for protecting corrodible metal structures such asthe interior surfaces of tanks.

The cathodic protection of tanks and compartments of ships, particularlyballast tanks which are filled with sea water, has been accomplished inthe past with some degree of success. In such cathodic protectionsystems the galvanic anodes are usually bolted to special anode hangerswhich project from the hull of the hip. Such installations requirescaffolding to attach each anode hanger to the hull and to attach anodesto the hangers. Repeated scaffolding in the tanks is not only expensivebut often times cannot be conveniently installed due to the maze ofcross bracing in the tank. Thus, the expense of achieving cathodicprotection in this manner often proves prohibitive.

Further, when the anodesare mounted on hangers attached to the hull,uneven protection often occurs due to the large current between theanode and that part of the hull which is closest thereto.

Another difficulty in connection with the installation of anodes onhangers is that the hangers are usually welded to the hull, and if thesteel adjacent to the weld crystallizes, and loosens the hanger, theanodes which are exposed to air may rub against steel and causesparking.

Accordingly, a principal object of this invention is to provide animproved means for providing cathodic protection to the interior portionof tanks or compartments.

Other objects of this invention are to provide means for effecting moreuniform, safer, and more economical cathodic protection to the interiorportion of tanks or compartments.

The above and related objects are achieved in accordance with thisinvention by mechanically and electrically conductively securing atleast one galvanic anode to an electrically conductive cable or wirewhich is electrically and mechanically secured to the lower portion ofthe hull. The other end of the cable is passed over a pulley which issecured underneath the deck supporting structure or top of the tank andthen is pulled taut and electrically and mechanically secured to thehull or tank wall. Guy wires may be connected between the hull and thepart of the cable carrying the anodes if needed. Since both ends of thecable are electrically connected to the hull, sparking between the anodeand hull is eliminated in case of a break in the cable to which theanodes are attached. Anodes may be replaced without the erection of anyscaffolding, since by loosening the end of the cable which is passedover the pulley, the portion of the cable bearing the consumed anodesmay be lowered to the bottom part of the hull where it is easilyreached.

Because the anodes may be centrally mounted or spaced in the tank orcompartment, more even cathodic protection is provided.

The invention as well as additional objects and advantages thereof willbest be understood when the following detailed description is read inconnection with the accompanying drawings, in which:

Fig. 1 is. a partial transverse section through a tanker showing, inelevation, the arrangement of galvanic anodes in accordance with thisinvention;

Fig. 2 is a partial sectional view taken along the lines 22 of Fig. 1;

Fig. 3 is an enlarged isometric'view showing the mean of attaching ananode to a cable, and

Fig. 4 is an enlarged view showing the means of attaching the anodecarrying cables to the walls of a ship tan or compartment.

Referring to Figs. 1 and 2, there is shown a compartment 10 in a ship12. A cable 14 having a plurality of galvanic anodes 16, such asmagnesium anodes, for example, attached thereto has one end anchored toa channel iron 18 in the lower part of the hull 20. The other end of thecable 14 is passed over a pulley 22 secured to the bottom of the decksupporting structure 24 and then is fastened to the lower portion of thetank bulkhead 26. Protection against side sway of the part of the cable14 carrying the anodes 16 is provided by guy wires 28 which extendbetween the cable 14 and the bulkhead 26 and hull 20 of the ship 12.Turn buckles 30 are provided along each brace line 28 to permit smalladjustments in the tension on the braces. Another turnbuckle 32 isprovided at the end of the cable 14 and is attached to the channel iron18 to permit a similar adjustment in tension on thecable 14. The cable14, as well as the wire braces 28 and sheave 22 may advantageously bemade of some corrosion resistive substance such as Monel metal or othernickel-copper alloy.

As is shown more clearly in Fig. 3, each anode 16 comprises a hollowsteel core 34 through which the cable 14 passes. The consumable metalportion 36 of the anode, usually magnesium, is cast around the core 34.The anode 16 is held in place on the cable 14 by wedges 38 which aredriven between the cable 14 and the core 34. Each wedge 38, which has aserrated edge 40which' makes contact with the core 34, provides themeans for making electrical contact between the anode 16 and the cable14. The number of anodes 16 which are attached along the cable 14depends on the current density and anode life requirements of theinstallation.

Fig. 4 shows, in detail, a suitable means for mechanically andelectrically securing the cable 14 to the bulkhead 26 of the ship. Theother end of the cable may be fastened to the hull in a similar manner.The end of the cable 14 is mechanically secured to the bulkhead 26, forexample, by being looped through the steel eye 42 and clamped back onitself by a cable clamp 44. A loop 46 in the cable 14 provides aconvenient way for attaching a block and tackle (not shown) to the cable14 when the anodes are to be lowered or raised. Other mechanical meansof securing the cable 14 could, of course, be used. The mechanicalconnection between the cable 14 and the bulkhead 26 is not relied uponto provide the electrical connection therebetween. between the cable 14and the bulkhead 26 is made by a bonding cable 48, usually made ofcopper, which is held in metallic contact with the cable 14 by the clamp50 and has one end 52 brazed to the bulkhead 26. As mentionedpreviously, the cable 14 is electrically connected to the hull orbulkhead at each point where it is mechanically secured thereto, thusavoiding the danger of sparks occurring between the magnesium anodes andsteel parts of the ship or tank in event the cable 14 breaks or comesunfastened. This arrangement is of considerable importance since anexplosive mixture of gas fumes may be present in the tank or compartment10. A loop 46 in the cable 14 provides means for connecting another lineto the cable when the anodes are raised or lowered into position.

The anodes 16 are installed by threading the anodes 16 onto the cable 14in the proper number and with the The electrical connection properspacing between anodes and electrically and mechanically. connecting thecable 14. and the anodes. 16 together, by means of the wedges 38, forexample. One end of the cable 14 is secured to the lower portion of thehull 20 and; theothei: end thereof is threaded through a sheave. 22= andis drawn towards its anchoring position on the bulkhead 26, raising theanodes 16 into position. The guy. wires 2& may be attached before theanodes 16 are raised, if desired. To replace anodes, the end of thecable which is anchored to the bulkhead 26 is unfastened and allowed torise (being paid out by. a block and tackle, for example), loweringthe.anodes to the lower part of the hull 20.. The. other end of the cable isdisconnected from its clamp allowing the consumed anodes to be removed.and fresh ones attached to the cable, which is raised into positionagain. No scaffolding is required to install anodes once. the cable 14is threaded through the pulley 22. There. may be as many cables 14.carrying the galvanic anodes 16 as are required to provide adequateprotection. For. the sake of simplicity in the drawings only a single.anode carryingcable 14 has been shown.

An installation of galvanic anodes in accordance with this invention iseconomical in that it requires but little scafiolding to make theinitial installation and no scaffolding to replace anodes. Because theanodes, in accordance with the method of the invention, may be securedbetween any two points between which a cable may be strung, the anodesmay be advantageously spaced with respect to. the surfaces they are toprotect. Thus, more even cathodic protection is provided and this, too,efiects an economy in the installation and maintenance of a cathodicprotection system. And, as previously mentioned, since each end of thecables 14 is electrically connected to the hull 20 or bulkhead 26, thedanger of sparking is eliminated even if the cable 14 breaks and permitsthe anodes 16 to bump against the steel in the tank or compartment.

Thus, the present invention provides an efficient, economical and safemethod. of cathodically protecting the interior surfaces of a tank or.compartment from corrosion due to. electrolytic action.

That which is claimed is:

l. A cathodic protection system for protecting. the interior surfaces ofa tank from electrolytic colrosion, said system comprising, within atank having a supporting member and an anchoring member, a pulleysecured to said supporting member, a metallic cable having its endportions detachably secured. to said anchoring member and itsintermediate portion passing through said pulley, a plurality ofgalvanic anodes, said anodes beingmechani- @1 13 a d, electr ll e ur dto Sa a l etw en n of said end portions thereof and said pulley, andmeans adjacent to each end of said cable for making positive electricalcontact between said cable and said anchoring member.

2. A cathodic protection system for metallic tanker compartmentscomprising a metallic cable, a plurality of galvanic anodes disposedalong a part of said cable and mechanically and electrically securedthereto, the end of said cable which is closest to said anodes beinganchored to a surface of said compartment, a pulley, said pulley beingspaced from the anchored end of said cable and secured to a surface ofsaid compartment, the part of said cable which does not have anodessecured thereto passing through saidpulley and being secured to asurface of said compartment, and means for electrically connecting saidcable to said compartment adjacent to where said cable is anchored andsecured thereto.

3. A cathodic protection system in accordance with claim 2, wherein eachcompartment contains a plurality References Cited in the file of thispatent UNITED STATES PATENTS Taylor Feb. 17, 1948 Tarr et al. June 29,1948 Robinson et al Oct. 9, 1951

1. A CATHODIC PROTECTION SYSTEM FOR PROTECTING THE INTERIOR SURFACES OFA TANK FROM ELECTROLYTIC CORROSION, SAID SYSTEM COMPRISING, WITHIN ATANK HAVING A SUPPORTING MEMBER AND AN ANCHORING MEMBER, A PULLEYSECURED TO SAID SUPPORTING MEMBER, A METALLIC CABLE HAVING ITS ENDPORTIONS DETACHABLY SECURED TO SAID ANCHORING MEMBER AND ITSINTERMEDIATE PORTION PASSING THROUGH SAID PULLEY, A PLURALITY OFGALVANIC ANODES, SAID ANODES BEING MECHANICALLY AND ELECTRICALLY SECUREDTO SAID CABLE BETWEEN ONE OF SAID END PORTIONS THEREOF AND SAID PULLEY,AND MEANS ADJACENT TO EACH END OF SAID CABLE FOR MAKING POSITIVEELECTRICAL CONTACT BETWEEN AND CABLE AND SAID ANCHORING MEMBER.